Metabolism impacts cellular functions and plays an integral role in human biology. This book presents metabolic regulation as a system, describing novel principles developed over the past several decades. It focuses on major metabolic pathways, including those that supply energy from ingested carbohydrates and fat and those of nitrogen metabolism involving amino acids and nucleotides. It covers glycolysis, mitochondria and energy production, enzymes and their inhibition, cellular signaling systems, energy, metabolomics, computer modeling studies, and medical issues related to metabolism.